234 MISSISSIPPIAN BBACHIOPODA 



1909. Camarotceckia persinuata Weller, Bull. Geol. Soc. Ana., vol. 20, 



p. 302, pi. 12, figs. 24-25. 



1910. Khynchopora persinuata Weller, Bull. Geol. Soc. Am., vol. 21, p. 



515. 



Description. Shell below medium size, subpyramidaal in form, wider 

 than long, the postero-lateral margins meeting at the beak in an obtuse 

 angle, the lateral margins rounded, the anterior margin straight. The 

 dimensions of an incomplete internal cast are : length 17 mm., width 20 

 mm., thickness 13.7 mm., width of sinus in front 11.5 mm. 



Pedicle valve depressed convex in the posterior half, with the surface 

 flattened or gently convex to the antero-lateral margins and somewhat 

 abruptly curved towards the opposite valve as it approaches the postero- 

 lateral margins, along the median line the surface is gently convex from 

 the beak to near the anterior margin where it is abruptly curved towards 

 the opposite valve ; mesial sinus originating near the middle of the valve 

 as a shallow, flattened depression which becomes gradually deeper ante- 

 riorly, towards the front it curves abruptly towards the opposite valve 

 and is produced in a broad, flat, lingual extension whose surface lies in 

 nearly a right angle to the plane of the valve and whose front margin is 

 deeply serrate ; the beak is small, sharply pointed, moderately incurved 

 and rather conspicuously extended beyond the opposite valve posteriorly ; 

 the delthyrium is broadly triangular, the deltidial plates and foramen 

 not observed; the plications rounded or subangular, simple, originating 

 at the beak, about seven usually present in the sinus and about seven or 

 eight upon each lateral slope, towards the anterior margin of the valve 

 they are frequently marked by a faint median longitudinal groove. In- 

 ternally the hinge-teeth are supported by dental lamella? which extend 

 from one-fourth to one-third the length of the valve anteriorly from the 

 beak, 



Brachial valve much more convex than the pedicle, becoming gibbous 

 in front, flattened in the umbonal region and sometimes with a slight, 

 longitudinal, median depression, the surface sloping with a long, gently 

 convex curvature to the front, the lateral portions of the valve strongly 

 convex longitudinally the anterior curvature being more abrupt, and 

 curving abruptly to the lateral margins; mesial fold obsolete in the pos- 

 terior half of the valve and only moderately elevated above the lateral 

 slopes in front; the beak strongly incurved beneath that of the opposite 

 valve ; the plications similar in form and number to those of the opposite 

 valve, and frequently grooved in a similar manner towards the anterior 

 margin. The internal characters of the species are not sufficiently well 

 known, but the cardinal process seems to be absent, and the hinge-plate 

 seems to be undivided, a median septum is present which is divided pos- 

 teriorly, each division supporting one side of the hinge-plate, the cavity 

 between the divisions of the septa apparently does not form an open crural 



